Inventors have recognized the effectiveness of the use of energy wave forms for medical treatment of various pathologies. Extracorporeal shock wave therapy (ESWT) is the non-surgical treatment of medical conditions using acoustic shock waves. Lithotripsy, the use of shock waves to fragment kidney stones, was introduced in Europe in the early 1980s, and by the mid-1980s shock wave lithotripsy had been established worldwide as the treatment of choice for disintegrating kidney stones. In 1986, European researchers conducted animal experiments which revealed that shock waves have the potential to stimulate bone formation by activation of osteoblast cells. The first positive results were reported after application of shock waves to artificial humerus fractures in rats. Since then, further experimentation with shock waves for other medical uses has continued, and today shock wave therapy has become an accepted method of treatment for a number of orthopedic indications. This method of treatment is increasingly popular with patients and physicians alike because it provides a non-surgical, non-invasive alternative for patients.
A shock wave is a type of acoustic energy resulting from phenomena, such as an explosion or lightning, that create a sudden intense change in pressure. The intense changes in pressure produce strong waves of energy that can travel through any elastic medium such as air, water, human soft tissue, or certain solid substances such as bone. Early approaches of using shock waves for medical treatment required immersing the patient in water and directing a shock wave, generated by an underwater spark discharge, at a solid site to be treated, such as a bone or kidney stone. When the shock wave hits the solid site, a liberation of energy from the change of acoustic impedance from water to the solid site produces pressure in the immediate vicinity of the site.
Three methods are currently used to create the acoustic shock waves for ESWT: (1) electrohydraulic, or spark gap; (2) electromagnetic, or EMSE; and (3) piezoelectric. Each is based upon its own unique physical principles. Spark gap systems incorporate an electrode (spark plug) to initiate a shock wave and ellipsoid to focus it. EMSE systems utilize an electromagnetic coil and an opposing metal membrane. Piezoelectric systems form acoustical waves by mounting piezoelectric crystals to a spherical surface.
In general, spark gap systems deliver the same level of energy as other methods produce, but over a broader area, and therefore deliver a greater amount of positive shock wave energy to targeted tissue. In spark gap systems, high energy shock waves are generated when electricity is applied to an electrode positioned in an ellipsoid immersed in treated water. When the electrical charge is fired, a small amount of water is vaporized at the tip of the electrode and a shock wave is produced. The shock wave ricochets from the side of an ellipsoid and converges at a focal point, which is the location of the area to be treated. Treatment areas are typically localized either by palpation or through the use of a fluoroscopy device.
The use of energy wave forms for medical treatment of various bone pathologies is known in the art. Some prior systems use ultrasound transducers, in direct contact with the skin of the patient, for transmitting ultrasound pulses to the site of the bone defect. Other devices utilize piezoelectric materials fastened adjacent to the pathological site on the patient's limb to produce ultrasonic energy in the vicinity of the bone pathology for administering therapy.
U.S. Pat. No. 4,905,671 to Senge et al. (“Senge”), issued on Mar. 6, 1990, teaches a method of applying acoustic shock waves to induce bone formation. Senge teaches that the acoustical sound waves previously used for treatment of bone have a generally damped sinusoidal wave form centered on ambient pressure. Senge differentiates an idealized shock wave from such acoustical sound waves in that the shock wave has a single pressure spike with a very steep onset, a more gradual relaxation, and virtually no oscillation to produce acoustic tension.
Senge utilizes the extremely short rise time of the shock wave to create high compression zones within bone tissue to cause restrictions of the microcompartments of the bone. Senge purports that such restrictions cause the formation of hematomas within bone, which in turn, induce the formation of new bone. Senge utilizes a shock wave source consisting of a spark gap between electrodes within a container of water. A metallic, ellipsoid-shaped structure surrounds a rear portion of the spark gap, opposite the patient, to produce a known focal point for positioning within the patient's pathological bone site. This device also requires that the patient be submerged in the water.
U.S. Pat. No. 4,979,501 to Valchanov et al. (“Valchanov”), issued on Dec. 25, 1990, teaches a method and apparatus for treating bone pathologies with shock or “impact” waves for correction of delayed bone consolidation and bone deformations. The method disclosed in Valchanov includes treating the affected bone site once or consecutively for a period of 10–120 minutes and subsequently immobilizing the limb for a period from 15 to 90 days. The impact wave generating device disclosed by Valchanov generally consists of a vessel which contains a transmitting medium or acoustic liquid such as water contained therein. At a bottom portion of the vessel are opposed electrodes which are adapted to produce a shock across the gap. Therefore, the patient is not submerged for treatment.
Other references, including U.S. Pat. Nos. 5,284,143, 5,327,890, 5,393,296, 5,409,446, and 5,419,327, teach the treatment of bone pathologies utilizing shock wave therapy in combination with imaging means for localizing the pathology during treatment. Still other devices utilize transducers for producing ultrasonic waves for therapy of soft tissue. These past methods for treating soft tissue surrounding bone utilized a transducer for the generation of ultrasonic waves for wave propagation into the pathological site within the soft tissue area. Furthermore, as described by Senge, clinicians traditionally implemented shock wave therapy for the treatment of bone.
Therefore, what is needed is a rapid, time-restricted and effective shock wave therapy treatment for pathological conditions not only associated with bones, but also bone and musculoskeletal environments and soft tissue.